Recovery of unsaponifiables from concentrates containing the same



Patented Sept. 9, 1952 L Racewa or UNSAPoNIFIABLEs FROM -CONCENTRATESJCONTAINING THE SAME Arthur Ira Gebhart, Union, N. J assignor to C01- gaterPal-molive-Beet Company, Jersey, (Jity, N'..J.,,a corporation of Delaware NoDra-wing. 'Application May 4,.1949,

Serial No. 91,421 gClaimjst '(01. 2eo 397.2

,The present invention relates to the recovery of, an unsaponifiable iraction, and more .p articur larly the selective recovery of sterols froman unsaponifiables concentrate containingfatty ma,- terial admixedtherewith.

Heretoiore, various means hav been. proposed for the separation of an unsaponifiable, concenw trate, and more particularly ahlghly concentrated sterol fraction. A common technique has been the use of molecular, distillation on the naturalfa-ts and oils, and; the recovery of anunsaponifiable fraction such as the. sterols f ro m the overhead. Such procedure is limited since the sterols for example occur, in they triglyceride inminute quantities (e. g. cholesterol occurs in animal oils and fats to the extent of. about 0.1 to

l-%), impuresterol mixturesaare obtained and only in fair. yield, and complex operating tech niques including short path high vacuum distil lation are required.

In processes involving;extractien wlth a solvent for the, unsaponifiables, (e; 5;, alcohol ,or ethylene dichloride), serious di ificulty is encountered in the presence of aa fatty material.

The fatty material (e. g. soap);-n1ay absorb,,dis I solve, or causeemulsification with the solvent to a-degree such that phaseseparation oi the solvent extract containing the unsaponifiables is diffioult, and extraction; is incomplete. Distillation techniques, arenot fully suitable-to recover particular fractions from the solventextract. Similarly, crystallization ,of unsaponifiables and more particularly sterols,-from the-solvent extract is not, economically practical on a commercial scale, as appreciable loss is encountered and impure products are recovered due to cc.- clusion, due, to the tendency of the unsaponifiables to remain in the fatty,ymaterialtinstead of crystallizing out because ofrtheirlow concentration, and due to concurrent precipitation of other acteristics of the solvent :in coniunction with the formationaand recovery of an insoluble steroloxalic acid complex. Accordingly, the solvent extra'ct may be reacted with. oxalic acid to form a separable oxalate complexwith cholesterol and similar types of sterols. These selected sterols 'mayrbe' recovered aspure compounds upon separation and decompositionof the complex. J As solvents, suitable liquid organic esters :may

beremployejd which dissolve the unsaponifiables including the sterolic material and are relatively poor solvents for saponified. fatty. material. It is preferred to use the lower esters containing not more than about eight carbon atoms in the molecule with at least two carbon atoms in. the acid radical moiety of the ester, More particularly the lower aliphatic esters, or, the lower fatty acid esters, having the above typestructure maybe selected for extraction purposes. For the re coveryof selected sterols from the solvent ex tract, by formation of an oxalate complex, it is desired to use generally such ester solvents which donot possess a free alcoholic or keto group,; e. g. lower fatty acid esters of lower monohydricf alcohols. Accordingly, such solvents asmethyl acetate, n-propyl acetate, isopropyl acetate, n,- butyl acetate and its isomers, amyl acetate, methyl amyl acetate, methyl propionataamyl propionate, ethyl butyratc, ethyl propionate, etc. may be used, but it is preferred to use ethyl acetategenerally. I

Themass suitable for extraction with ethyl acetate or, similar solvent is an. unsaponifiable concentrate, more specifically a sterol concentrate, having saponified fattymaterial admixed therein. These concentrates in addition to sterols may contain a number of" other sub:- stances such as, tocopherols, vitamins, oils, phosphatides, pigments, etc. Such concentrate sof unsaponifiables or sterols may be derived generally either from the splitting (e. 'g. hydrolysis, saponification, etc.) of a fat, fatty oil, or fatty wax of animal, vegetable, or marine origin and the subsequent removal of a portion of the, split fattymaterial, or by the separation of at least a fraction of the fatty material without decomposition, e. g. solvent, fractionation, to obtain thereby thedesired unsaponifiabletor sterolconcentrate in each instance. More specifically, these concentrates may be derived from such fatty materialsas tallow, lard, W001 fat, halibut liver oil, tall oil, wheatlgerm, cottonseed, soy- ,bean, rapeseed and cocoa butter, In general, cholesterolmay be recovered from the sterol concentrates derived from ,fatty materials of animal origin, andparticular phytosterols such as stig} ,masterol, may be obtained from concentrates emanating from vegetable materials by practice of 3 the various features of the present invention.

Accordingly, the present invention contemplates the useof concentratesresulting from hydrolysis oithe natural fats, fatty oils, andfthe like in any suitable manner, and the removal of ,the',major portion ,of thehfatty acids: and/or glycerine -therefrom. The still bottoms lesllltin .fromthe distillation of theproductslof continuous Counter-current high pressure fat-splitting operations, are preferred, such ,as the process s illustrated by Ittner, U. SqPatents Nos. 2,435,745 and 23:58 wMore particularly it Tisdesiredito use the second bottoms obtained by recycling the original still bottoms through the splitting zone.

There is thus recovered an enriched bottoms ,7

fraction which usually contains over 5% sterols by weight. A sterol concentration of at least about 5% is efficacious since the losses during processing are thereby of a relatively small order.

After the practice of such hydrolytic proce-' dures followed by distillation, a concentrated phase containing fatty acids, sterols, some glycerine, and minor amounts of other constituents tion equally well in solvent extraction of dried soap material. The proportion of alkaline saponifying agent is variable, depending upon the extent of saponification desired. Generally, at least a molar equivalent (and preferably an exwill remain in the still. The major portion of fatty acids and glycerine may be or may have been distilled at either atmospheric or reduced pressure in any suitable-manner, leaving a dark colored residue containing significant amounts of fatty acids and in which the unsaponifiables and particularly the sterols have been concentrated.

Similarly, the reaction products obtained by alcoholysis of a fatty material, as indicated by Allen et al., U. S. Patent No. 2,383,579; Dreger, U. S. Patent No. 2,383,596 and Trent, U. S. Patents Nos. 2,383,632 and 2,432,181, may be utilized to obtain the sterol concentrate. The alcoholysis reaction products may be flash distilled directly from the alcoholysis zone to separate unreacted alcohols, esters, and glycerine, whereby a concentrated residue is obtained containing the sterols and other unsaponifiables as valuable by products. Alternatively, the reaction mixture containing chiefly the esters, fatty acids, and glycerine, may be subjected to phase separation whereby there are recovered separate ester and glycerine layers. The fatty acid esters and/or glycerine in each layer, may be removed in any suitable manner such as by either batch or continuous distillation. The residues after separation of these and other volatile constituents may be admixed, if desired and consist of a relatively small volume of material containing generally unreacted fatty acidglycerides as well as the sterols in a high concentration and unimpaired condi tion.

Likewise, the sterols may be found concentrated in the extracts or ramnates from the solvent treatment of fatty materials. The 1 efficacy of liquid-liquid extraction as a means of fractionating fatty mixtures is favorable for the selective separation or concentration of the unsaponifiable or sterol content in a particular phase. Par ticularly suitable for the recovery of a concentrate are the counter-current fractionation processes for fatty materials using a oneor two-solvent system. The solvents may be strongly or weakly polar, or non-polar in character. The solvents which appear most suitable are furfural, the hydrocarbons such as hexane, and the liquified normally gaseous ones including propane, butane, etc. With solvents such as propane, appropriate adjustments-of temperature and/or pressure are necessary inorder" to recover the desired concentrate. Any solvent in the layer containing the sterols may be removed in any suitable manner.

The still residues and other sterol concentrates containing non-sterolic material, e. g. fat.- ty acids and/or their esters,-may be saponified in any manner, either by batch, semi-continuous or continuous operations. The ysaponification may be accomplished by means of 'a" suitable basic saponifying agent, such as those having an alkali metal as the cation, e. g. sodium hydroxide, potassium hydroxide, or'sodiu'm carbonate. These alkali metal bases are highly desired beesters, present in the still residues.

'sults.

cess) of saponifying agent is utilized in order to insure complete saponification of the free acids and the fatty acids in combined form, such as in the form of esters of the sterols and other It is preferred to convert the bottoms to soap by the usual type of kettle boil method, wherein the saponiflable material is boiled with strong aqueous alkali in order to effect saponification. After graining, washing, and settling with or without nigre removal, the resulting soap may have a concentration of total fatty acids (as soaps) and unsaponifiables of higher than by weight.

A sufficient amount of water or an aqueous solution may be added to the saponified' mass containing the unsaponifiables to form a liquid soap which does not gel to a solidified mass upon cooling to room temperature. Generally, a clear homogeneous liquid results upon addition of the requisite amount of water. Occasionally, certain soap batches when thus treated may have a minor amount of soft, gelatinous masses dispersed in the aqueous solution at room temperature. However, upon the addition of ethyl acetate or other ester solvent, these masses rapidly disintegrate in the surrounding soap solution. More particularly, about 10 to about 20% concentration in the solution of T. F. A. 8: U. as hereinafter defined is usually required for successful extraction of saponified still bottoms from fats, particularly animal fats such as tallow. More preferred concentrations productive of particularly efficient results is from about 15 to about 18% T. F. A. & U. V

The requisite dilution of the unsaponifiable concentrate containing the saponified fatty material, e. g. the kettle soap mass, is of material consideration in order to achieve the desired re- At higher concentrations, the soap containing mixture tends to gel or solidify. In addition at such higher concentrations, troublesome emulsions forming at the interfaceof the solvent and soap solutions in continuous counter-current liquid-liquid extraction, are encountered and may prevent successful and efficient extraction with the ethyl acetate or similar solvent. Other dilute concentrations such as those below about 15%, and more particularly below about. 10% are not particularly desirable though extraction can be successfully carried out. Where .very dilute concentrations are employed, the mutual solubility of ethyl acetate in water (approximately 8% at 25 C.), the solubility of water in ethyl acetate (approximately 3%), and the considerably greater solubility of ethyl acetate, in the soap solution results in increased amounts of solvent in the aqueous phase. Moreover, the

time required to extract a given quantity of the unsaponifiables is increased materially, thus, decreasing the efficiency and economy of. processing desirable for commercial operations.

The soap solution at the desired concentrations has a dark brown color, a pH of about 9.5 and remains essentially liquid at room temperature. In batch type operations, the solution isextractedwith ethyl acetate using about one part of though the solvent 'ratlof is. not critical and: can

vary to the useof an equal volume/or several volumes of solvent per volume of solution if. desired. 1 Itisthus possible'to extract considerably over:90% of-thetotal'unsaponifiable content,.and even over'98%., The crude ethylaacetate ortsimilar solvent extract-derived from split tallow bottom's usually contains about 30. to. about 40% cholesterol and a" percentage offree fatty acids that may totalabout and even in certain instancesrun as high as to fattyaacids in the extract. Such free. fatty. acidsresult from hydrolysis of the soap solution duringsolventte'xtraction. It has been discovered moreover that these fatty acids do not interfere with the-recovery'of sterols such as cholesterol from the extract. If desired however, the free fatty acids may be removedv by washing with a fatty acid neutralizing agent'such' as sodiumcarbonat'e or sodium hydroxide. Thisextraction procedure may be utilized ina continuousand counter-currentmanner with ad.- vantage. Basically, suchprocedure involves the use: of a-counter-current extraction tower where.- in the soap or soap solution i'sf flowed intotthe upper-"portion of a vertical extraction tower by any convenient means, such as by gravity or pressure. The solvent comprising ethyl acetate issimilarly inserted at a point below the pointof introduction of the soap solution. These liquid phases flow counter-currently whereby an extract comprising theunsaponifiables is recovered at the top and the raflinate containing the spent soap" solution and a minor amount of solvent is removedfrom the bottom. Thesystemis preferably operated at. normal atmospheric temperature and pressure. However, slightly elevated temperatures approximating the boiling point of ethyl acetate are suitable. A temperaturegradient-in the tower may be maintained by suitable apparatus in or aroundthe tower and/or a reflux may be used byrecycling into the extraction towerafracti'on of the extract, to aidinrectification of the rising extract phase.

For a complete and unitary continuou zextraction process, it is preferable to attach various unitstothe extraction apparatus such as awashing tower containing a ratty acid neutralizing agent, a-- water scrubber to remove any minor amounts-of soap in the extract, evaporatingand distillin units for the removalofwater and recoveryof solvent, etc;

The soap solution remaining after the extraction of the-unsaponlfiablescontains a minorproportion of solvent. This solvent can be recovered for example by a variety of methods, including distillation and fractionation. A more satisfactory'procedure is to acidify the spent soap, separate the fatty acid. layer, which contains about 9.5% of the totalsolvent from the extracted soap solution and recover the solvent from this .fatty acid-layer. The aqueous phase,. containing. some dissolvedsolvent, can be neutralized, e. g. with sodium carbonate, and used for diluting'succeede ing soap masses. The recycling of the spent aqueous phase is advantageous for continuous processing and for maximum recovery as. it conaera ed addition complexes maybe .aformedlandirecoveredi from the: solvent extract. Thepresenceorsignificantlam'ounts of free water in thessolvent extract" inhibits the formation. andseparation of the tract resulting from either batch or continuous.

extraction such asdescribed aboveis-treated'in any suitable manner to substantially remove-thewater and to form therebyasubstantially anhydrous solvent extract. Areature or the-usesoi thef estertype solvents utilized herein isith'e fact that such solvents'genera'lly form azeotropes with water,-and-thereby facilitate the removal of water and the preparationof asubsta'ntially anhydrous extract: Thus, the wet unsa'ponifiable solvent extract can be distilled until a substantially anhydrous extract remains. In this distillation operation the-water 'is removedazeotropically with the'solvent generally. Whereethyl acetate is the specific solvent, the ethyl acetatezwater azeotrope contains about 8.2% by weight ethyl acetate and boils at 70.4" C., whereas anhydrous ethyl acetate boils at 77.0 C. Illustratively, other ester; solvent':water azeotropes are a n-propylacetate:waterazeotrope boiling at 82.4 C., an isopropyl acetatezwater azeotrope boiling at 75L0 C., a n-butyl acetate:water azeotains relatively small but significant amounts of trope boiling'at92.0C.,etc; By removal of the water and control of the amount of solvent present in and distilled from the extract, the unsaponifiable content of the l cit-cholesterol (or similar sterol capable of form ing the oxalatecomplex) by the digitonin method anda suitable quantity of substantially anhydrou'soxalic acid (0.7 mole for example) per 'mol'e ofcholesterol or similar sterol is added to the extract, which is then heated under reflux'iora short time to effect complete solution ofthe oxalic acid. The acid ratio isnot criticaland it is preferred to use a lareeexcess ofoxalic-a'cld above the stoichiometric amount of 0.5 mole acid per mole of reactive sterol, of the order ofat least about a 40% excess (0.7 mole). The oxalate complex is relatively insolubleiin the solvent extract and tends to'preci'pitate 'f-rom solution. Preferably the solution may be cooled to induce more complete precipitation of the complex. Upon cooling at room' temperature for example, the oxalate complex crystallizes: out and is collected on a filter. Aside from whatis retained by adsorption of mother liquor: onthe crystals, all of :the dark coloredproducts in the After washing extract pass into the filtrate. with a small quantity ofzdry ethyl acetateor other suitable solvent such as petroleum ether, the oxalate complex has a light tan or white color. If desired, the oxalate complex may be recrystallized from hot ethyl acetate solution or other suitable solvents which, after. an optional treatment .with activated carbon to decolorize the solution, deposits pure white crystals upon cooling. to. room temperature (approximately 25C.) and below, l

The oxalate addition complex may be. rapidly decomposed in. any suitable manner as by alcohols, acetone, and water to yield the cholesterol 01 similarsterol andioxalic acid. .A preferred procedure. ,h-owever,iis the formation of, a solu-v tion. :of the. purified complex. in .ethyl :acetate, suchg-as .ail5 to 20 solution, to which. about 25% of water is added. Upon heating. under r-e-. fluxsforflrabout fifteen minutes, separatingthe water layer and subsequently washing with warm Water,substantially-.alliof the oxalic acidmay be removed from the mixture. On cooling to about 40 ;C.,- thecholesterol ,(or similar type sterolwhich had been liberated fromthe complex) beginstocrystallize from the washed acetate. If desired the recovered cholesterol or other sterols may be recrystallized from ethyl acetate-or other suitable solvents. The recovery from-the oxalate appears to be practically quantitative and puresterol products may be obtained in .this' manner. For example, cholesterol of U. (S.; P. standards may be recovered from the; bottoms, resulting from the splitting. f .tallow. An alternative procedure after saponification ofthe bottoms and finishing of the. soap as. previously set forth is theconversion of the saponified mass to a substantiallydry condition in any suitable manner, such as drum drying, or spray drying. The moisture content of. dried soap mixtures of this character averages a few per cent (about 3 to 5%) in conventional practice. The dried soap may bjeground and/or screened to small particles in ordert-o increase the efficiency of subsequent solvent extraction. If desired .the soap particles may be in the: form or shape of chips, spheres, flakes, granules, etc. Thecrude solid particles may thereafter, be subjected to solid-liquid phase extraction with ethyl acetate or similar type solvent as the sterol solvent by'either batch or continuous, including counter-current, operation. The preferred operating procedure howeverinvolve the vigorous agitationof the dried soap part'icles.-with ethyl acetate at slightly elevated temperatures, and more particularly. even at temperatures approximatingorat the boiling point of the solvent. The extract maybeseparated by any means suitable for solid-liquid phase 'separatiom in: eluding .gravity, filtering, centrifugal force, etc. It has been. found that after filtering, .-and ;repulping the filtercake if desired, about 90% of the total unsaponifiable contentmay .be recovered in theextract generally. v

Saponificati-on procedures for the original unsaponifiable concentrate containing saponifiable fatty. material by means of which a substantially anhydrous pr'oduct is obtained directly may be used advantageously. -..Such operations may be batch or continuous and. involve generally saponification of. a fatty material with alkali during passage through a series of heating coils. .An almost anhydrous soap mass is recovered from a flash chamber where water and any other volatile constituentshad been vaporized and removed. from the saponificatio-n mixture. These processes are well known in the art, and may be operated below thedecompositionpoint-of the sterols or other unsapo-nifiables desired to be recovered subsequently. r. 1

It is' also possible to preparea substantially anhydrous soap mass and condition the same r in order: to initiate the; saponifi'catio-n: reaction.

Thereafter with agitation .the ex-othermicfheat of saponification .is utilized; to continue the ree action and Eto vaporize-the. moistur.e;..1 Vacuum may :be' used if desired the reduced. pressure facilitates .theflashing off of. the water. In-the coursejofj the. reaction; the soap masses ;;or lumps which are formed are progressively broken up until the soap is in theform of granules. When the saponification step is complete, the substantially dried soap productdn'powdered form may be recovered and submitted to solvent extraction as previously set'forthf Where concentrated unsaponifiables 'or sterol residues are obtained with the fatty acid-Eradicalsxsubstantially. combined as soap, it isnot generally necessary to-perform the saponification step. Such a suitable concentrate which also constitutes arich source of sterols is a soap stockobtained from the alkali refiningof. fats and oils. The alkali refining (either wetv or dry) procedure is well; known andv widely '.used throughout the art, and-as, such forms no'part of; this invention, The-roots which result from such treatment with. alkalis (e. g. caustic soda, soda ash, andgtheirmixtures), contain .asig nificant .portion of. the total sterol contentpresentgin the original fats and oils. For'example, the soap stock from; alkali refinedsoybean may contain as muchias 2 or 3% sterols by Weight. If suitably dry, vthesoap stock may be extracted directly with the solvent;-or the soap stock may be subjected to a drying operation before ,.ex traction where such procedure. appears desirable; Alternatively. the soap stock may be diluted to the suitable concentration range so as to avoid formationof a gelled solid and this relatively .dilutemsoap :mixture may subsequently be extracted with solvent aspreviously indicated. The/soap stock obtained from the ,refining of vegetablev oils, .and'. particularly soybean oil, are valuable-for their content of phytosterols. Vegetable. sterols capablexof forming an oxalic acid'complex' such as stigmasterol, maybe recovered in high purity and yield'by the present invention. 7, a q The footsv obtained i from refining .offatty coils and the like-by hydration (e; g. water refining); contain.=signific ant amounts of unsaponifiables including sterolic materiaL- Such foots maybe added to the soap stock derived'from alkalirefining of fatty material, and the entire; mixture may be processed by any of the aforesaid extractionprocedures.

, Where the unsaponifiable or sterol concene trates, have a significant-amount of the-total sterols in combined form; such as sterolic esters of fatty acids, sterolglucosides, etc., it3 is generally desirable todecompose the ester or other type linkage prior to extractionin any suitable manner, as by saponification or hydrolysis, 'in order to have. a fmax'imum free *sterol' content in the original concentrate and accordingly, a maximum amounto'f sterols recovered in-the solvent extract. I I

The following "are additional specific examples designed to be illustrative-of the nature of the invention:

Example I .Preparation of kettle soap from splitter second bottoms 1 A'ba-tch of splitter second still bottoms derived from tallow is kettle'boiled in a small 's'oap kettle.

Ten pounds of bottoms are boiled with 3.5 lbs of 50" Be. NaOH excess) for three hours. The soap mass is grained with solid sodium chloride, and the clearlye is removed. The soap mass is taken up in waterand is boiled again for one hour and grained. The washing, boiling and graining arerepeated once more and the final. soap settles overnight in a hot room. The io1-' lowing day the separated soap is roll dried. There is recovered 10 lbs. 4 oz. of dry soap..

The analysis of thebottoms used is as follows:

Percent A. V. (KOH) 9.56 S. V. (KOHM 14.96 I. V 58.50 Unsap. 16.63 Glycerine 0.25

Ash 0.43

Analysis of'the finished roll dried soapis as follows:

T. F. A. & U. i. 83.90 Unsap. in T. F. A. 8; U. 12.20 Free cholesterol in T. F. A. 8: U. 6.51 Total cholesterol in T. F. A. 8z U. 6.64

. vMoisture isnot determined on this lot of dried soap but from previous experience it would be in the neighborhood .of 2.5to3.0%. Free'alkali would be less than 1% as NazO.

The dried-soap is screened through a 12 mesh screen before extraction. 1

Example II.--E:ctra ction jromdried soap 200 m1. of'anhydrous ethyl acetate, there is added a solution of4.6 g. of anhydrous oxalic acid in '75 ml. of ethyl acetate. The solution is refluxed 5 minutes to dissolve the oxalic acid, and left to cool at room temperature whereupon a cholesterol-oxalate complex crystallizes out as a solid phase. The crystallized oxalate is filtered by suction, washed with two; 5 ml. portions of anhydrous ethyl acetate and 20.6 g .of oxalic complex is recovered. After distilling off 200 ml. of solvent from the filtrate and washings, an additional 2.2 g. of oxalate complex separates on cooling.

"The total amount of oxalate complex (22.8 fig.) is, dissolved in ethyl acetate tofo'rm a%solution to which of water is added. The solutionis refluxedfor 15 minutes and a water Per cent layer separated therefrom. 1 The ethyl acetate layer is washed with warm water. and the water layer is removed again to remove all of the oxalic acid. On cooling to 40 C., cholesterol is crystallized out from the washed ethyl acetate. The yield of cholesterol is 204g. from the 22.8 of cholesterol-oxalate complex. 1 1

Run. 2.--This run is made with 500 g. of soap in the same manner as thefirst one but the soap is onlyextracted twice, the first time for 30. minutes and the second time for 10 minutes.

The oxalate may be prepared'from this extract in the manner described above. Example lllr Elrtraction from g solutions A 625, g. sample of soap solution (125 g. T. F. A. &U.) containing 16.25 g. of unsaponifiables and 8.12 g. of cholesterol is shaken out with four 1250 ml. portions of ethyl acetate, shaking for three minutes ach time.

Each extract is recovered and analyzed and the aqueous soap following results are obtained:

fiablesora total or 610g. The extracts obtained are as'follows:

-Wight. of final wet filter'cake 693g. Weight of final dry filter cake-407 g.

To the 54.5 g. of extracted solids dissolved in A totalof 7.4 g. of cholesterol is recovered corresponding to 91.0% of the total present.

Emammle I V The soap is prepared from first still bottoms resulting from the splitting of tallow. The analysis of the final soap solution is as follows:

Percent T. F. A. &U.. in soap solution 23.30 Unsap. in soap solution 8.87 Cholesterol in soap solution 0.84

This corresponds to 3.6% cholesterol content in theT. F. A. 8: U. which is roughly half the amount usually found in second bottoms.

Escample V.-Gontinuous extraction 7 The soap solution is prepared by kettle saponification of second still bottoms resulting from the splitting of tallow. The analysis of the soap solutionis as follows:

V Pounds Soap solution 1;- 750.0 T, F. A, 8; U. 112.5 Unsap. in T. F. A. 86 UK 14.5 Cholesterol in T. F. A. & U. 7.35

The above soap solution containing by.

weight T. F. A. & U. is submitted to continuous extraction with fresh ethyl acetate for 5l/4'hours at a'rate of 500 lbs. of ethyl acetate per hour and the ethyl acetate extract is separated continuously. I

The ethyl acetate contains 3.4 pounds of fatty acids, 13.2 pounds of unsap'onifiables, and 6.61 pounds of cholesterol in said unsaponifiables. Free water is vaporized s an azeotrope with ethyl acetate and the concentration of unsaponifiables is adjusted until the solution contains unsaponifiables. Anhydrous oxalic acid in an amount 40% in excess of the quantity theoretically required-for complete reaction with the cholesterol is added, and the solution is heated under reflux for lominutes. Upon cooling and standing at room temperature (25 0.), 4.5 pounds of oxalic complex precipitates as white crystals and is recovered by filtration." Upon decomposition with hot Water, there is recovered 4.0 pounds cholesterol having an uncorrected melting point of 146147 C.

The yield of cholesterolmay be increased by further extraction of the spent soap solution with ethyl acetate, and/or by recycling the same to a succeeding batch as previously indicated.

Ecvample VI .--C'ontinuous counter-current extraction The soap solution is derived from kettle saponification of tallow second bottoms and analyzes as follows:

Soap solution pounds 672.0 T. F. A. 8: U. per cent 14.9 Unsap. in T. F. A. & U. do 12.24

Cholesterol in T. F. A. 8; U. do 5.24

A column 12 feet high, 6 inches in diameter and I packed with /2 inch Raschig rings is utilized for the continuous counter-current extraction. The soap solution is introduced about 18 inches from the top at a rate of 300 cc. per minute, and wet ethyl acetate (3% water) is introduced 18 inches from the bottom at a rate of 600 cc. per minute. The spent soap solution is drawn off from the bottom of the column continuously, so as to hold the interface about 1-2 inches from the top of the tower.f The soap solution is in the continuous phase, and the ethyl acetate bubbles through as droplets. The extraction is conducted at room temperature and normal atmospheric pressure.

The ethyl acetate extract continuously overflows from thetop of the tower into the bottom of a water wash tower which is 10 feet high, 3 inches in diameter and packed with inch Raschig rings. The extract is washed continuous- 12 ly with water pumped into the top of the tower at 60 cc. per minute. The interface isykeptat the top of the tower by regulating the withdrawal of the aqueouslayer from the bottom. The washed extract overflows into a stripper where the water and most of the ethyl acetate is distilled and their vaporsconducted into a condenser. Thejanhydrous ethylacetatesolution containing about 25% solids is withdrawn from the bottomof the stripper. x The spent soap solution from the'bottom of the extraction tower is run continuously into a small tank and mixed therein with some dilute sulfuric acid until a pH of about 5 is obtained. The soap is split thereby into two phases,lthe upper. layer containing fatty acids and -ethyl acetate, and the lower layer containing. water and ethyl acetate. The layers are separated continuously in a phase separator, the aqueous layer withdrawn from the bottom and the fatty layer overflowing into a steam heated double pipe from which a mixture of ethyl acetate vapors and liquid fatty acids are discharged into a separator. The ethyl acetate vapors are recovered in a condenser and the fatty acids free of ethyl'acetate are withdrawn. from the separator.

The 672 pounds of soap solutionoriginally con tained 5.24 pounds cholesterol. There is 4.89 pounds of cholesterol in the extract and .35 pound in the spent fatty acid layer. This represents a yield :of over 93% cholesterol inthe extract.

The cholesterol may be recovered from the ex.- tract by means of the oxalate complex in the manner described in Examples-I and V. In conclusion, it may be noted that the multiple function of ethyl acetate and similar ester solvents in the relationship set forth is most conducive to the performance and attainment of a successful procedure capable of commercial oper-- ation. They are quite suitable for the extraction of an"unsaponiiiable fraction containing stero ls from "a concentrate, without being good solvents for constituentsthat may' interfere in subsequent processing operations; troublesome emulsions and formation of gels and solids are avoided by their proper use; residual water may be distilled off as an azeotropic mixture with a minor proportion of the solvent with obvious advantages they are excellent solvents for oxalic acid and relatively poor solvents for the oxalic complex; relatively large yields and pure products are attained by their use even in commercial operation, etc.

Where reference may be made in the description and/or the claims to fatty material, it is of course intended to include the equivalent fats,

fattyoils and waxes, free fatty acids and/or fatty acids chemically combined such as in the form of esters, salts, etc. The term still bottoms includes the crude residues containing concentrated unsaponifiables suchas a sterol concentrate, and also residual fatty material remaining after the removal by distillation or evaporation of a major portion of vaporizab-le fatty material. Where reference is made to anhydrous oxalic acid, it is intended to exclude the complete use of oxalic acid having water in combined form in the molecules, e. g. water of hydration. :The phrases substantially anhydrous solvent extract, substantially anhydrous ethyl acetate extract, or their equivalent, do"

not exclude the presence of such minor amounts of water as do not cause material decomposition of, nor prevent extensive formation nor separation of the oxalic complex'since excess oxalic acid may act as a dehydrating agent by formation of a dihydrate. In thesymbol "T. F. A. & 17., T. F. A. refers to the total fatty acid content whether in the form of, free-fatty acids or combined as soap, sterolic esters, etc., and, ,U refers similarly to the unsaponifiable content whether sterolic or non-sterolic in nature. -All percentages and proportionsillustrated are by weight unless otherwise specified.

Since certain changes may be made in carrying out the above process without departing from the scope of the invention, it is intended that all matter contained in the above description shall be interpreted as illustrative and not in a limiting sense.

It is also to be understood that the following claims are intended to cover all the generic and specific features of the invention herein described, and all statements of the scope of the invention, which as a matter of language might be said to fall therebetween.

Having described the invention what is claimed as new and desired to be secured by Letters Patent is:

1. A process of recovering cholesterol from tallow fatty acid still bottoms which comprises saponifying said bottoms to form water soluble soaps of the saponifiable material therein; purifying said saponified bottoms by washing, graining and settling to obtain a settled soap; preparing a dilute aqueous solution of said settled soap; extracting said settled soap solution with ethyl acetate to obtain a wet ethyl acetate solution of sterols; removing at least substantially all the water from said solution by azeotropic distillation; reacting cholesterol in said solution wth oxalic acid under substantially anhydrous conditions to form a complex; separating said complex; and decomposing said complex to recover said cholesterol.

2. A process of recovering sterol from fatty acid still bottoms which comprises saponifying said bottoms to form water soluble soaps of the saponifiable material therein and preparing an aqueous soap mixture of the saponified bottoms.-

extracting said aqueous soap mixture with a liquid ester of a lower fatty acid having at least two carbon atoms and a lower monohydric alcohol to obtain a wet solution of sterol, removing at least substantially all the water from said solution, reacting sterol in said solution with oxalic acid under substantially anhydrous conditions to form a complex, separating said complex, and decomposing the same to recover sterol therefrom.

3. A process of recovering sterol from fatty acid still bottoms which comprises saponifying said bottoms to form water soluble soaps of the saponifiable material therein, preparing a liquid aqueous soap mixture of the saponified bottoms, introducing said liquid aqueous mixture into an extraction zone, introducing as a sterol solvent a liquid ester of acetic acid and a lower monohydric alcohol into said extraction zone below the level of introduction of said aqueous soap mixture, flowing the two liquid phases countercurrently, removing from said zone a wet solution of sterol in said solvent, separately removing from said zone a raffinate phase containing the spent soap, removing at least substantially all the water from said solution, reacting sterol in said solution with oxalic acid under substantially anhydrous conditions to form a complex, separating said complex, and decomposing the same to recover sterol therefrom.

4.A process "of .recovering sterolfroma sterol concentrate having a major proportion of soap in admixture therewith which comprises extracting said concentrate with a liquid sterol solvent, said solvent being an ester of a lower fatty acid and a lower monohydric alcohol, separating a solvent extracthaving sterol dissolved therein, reacting sterol in said solvent extract with oxalic acid under substantially anhydrous conditions to form a complex of said acid and sterol, separating said complex, and decomposing the same to recover sterol therefrom.

5. A process of recovering selected sterols from still bottoms comprising a major proportion of saponifiable material and having sterols concen trated therein which comprises saponifying still bottoms with an alkaline saponifyingagent to form soaps thereof in admixture with said sterols, extracting said saponified bottoms with a liquid sterol solvent, said solvent being an ester of a lower fatty acid having at least two carbon atoms and a lower monohydric alcohol, separating a solvent extract having sterols dissolved therein, reacting selected sterols in said solvent extract with oxalic acid under substantially anhydrous conditions to form a complex of said acid and selected sterols, separating said complex, and decomposing the same to recover the sterols therefrom.

6. A process of recovering sterols by solvent ex traction from still bottoms comprising saponifiable material and having sterols concentrated therein which comprises saponifying said bottoms and adjusting the water content thereof to a concentration of up to about 20% total fatty acid and unsaponifiables content by weight whereby a liquid soap mass is obtained which does not gel to a solidified mass in the presence of the solvent, extracting said liquid soap mass with a liquid ester sterol solvent of a lower monohydric alcohol and a lower fatty acid having at least two carbons, separating a solvent extract having sterols dissolved therein, and recovering said sterols.

7. A process of recovering sterol by liquid-liquid phase solvent extraction from a mixture of water and a sterol concentrate having a major proportion of soap and a minor proportion of unsaponifiables which comprises maintaining said mixture as a flowable liquid with sufficient water to prevent the presence of substantial amounts of gelled saponified fatty material in said liquid mixture during extraction, subjecting said liquid mixture to liquid-liquid phase extraction with a liquid lower aliphatic ester sterol solvent having at least two carbon atoms in the acid radical whereby sterol is extracted from said mixture anddissolved in said solvent in the absence of substantial gelled saponified fatty material and without substantial emulsion formation, separating and recovering a solvent extract having sterol dissolved therein.

8. A process of recovering sterol from still bottoms containing the same, which comprises saponifying aid bottoms to form water soluble soaps of the saponifiable material therein, forming a dilute aqueous soap mixture of said saponified bottoms, continuously introducing said soap mixture into an extraction zone, continuously introducing as a sterol solvent a liquid ester of acetic acid and a lower monohydric alcohol into said extraction zone below the level of introduction of said soap mixture, flowing the two liquid phases countercurrently, removing from said zone a solvent extract phase with sterol dissolved therein, separately removing from said zone a raflinate phase containing the spent liquid soap mixture and "recovering said sterol from said solvent extract phase.

ARTHUR IRA GEBHART.

, REFERENCES CITED" of recoi'd in the Number 16 UNITED STATES PATENTS Name Date Gams Oct. 22, 1929 Mi1a,s Sept. 19, 1939 Porsche Feb. 20, 1940 Julian Oct. 22, 1940 Fernholz Apr. 28, 1942 Yoder Nov. 14, 1944; 

1. A PROCESS OF RECOVERING CHOLESTEROL FROM TALLOW FATTY ACID STILL BOTTOMS WHICH COMPRISES SAPONIFYING SAID BOTTOMS TO FORM WATER SOLUBLE SOAPS OF THE SAPONIFIABLE MATERIAL THEREIN; PURIFYING SAID SAPONIFIED BOTTOMS BY WASHING, GRAINING AND SETTLING TO OBTAIN A SETTLED SOAP; PREPARING A DILUTE AQUEOUS SOLUTION OF SAID SETTLED SOAP; EXTRACTING SAID SETTLED SOAP SOLUTION SOLUTION OF STEROLS; REMOVING AT LEAST SUBSTANTIALLY ALL THE WATER FROM SAILD SOLUTION BY AZEOTROPIC DISTILLATION; REACTING CHOLESTEROL IN SAID SOLUTION WTH OXALIC ACID UNDER SUBSTANTIALLY ANHYDROUS CONDITION TO FORM A COMPLEX; SEPARATING SAID COMPLEX; AND DECOMPOSING SAID COMPLEX TO RECOVER SAID CHOLESTEROL. 